Classical conditioning in oddball paradigm: A comparison between aversive and name conditioning.

The nature of cortical plasticity in learning is one of the most intriguing questions of modern cognitive neuroscience. Classical conditioning (as a typical case of associative learning) and electroencephalography together provide a good framework for expanding our knowledge about fast learning-related cortical changes. In our experiment, we employed a novel paradigm in which classical conditioning was combined with passive oddball. Nineteen subjects participated in the first experiment (aversive conditioning with painful shock as unconditioned stimulus (US) and neutral tones as conditioned stimulus (CS)), and 22 subjects in the second experiment (with a subject's own name as US). We used event-related potentials (ERPs) and time-frequency analyses to explore the CS-US interaction. We found a learning-induced increment of P3a in the first experiment and the late positive potential (LPP) in both experiments. These effects may be related to increased attentional and emotional significance of conditioned stimuli. We showed that the LPP and P3a effects, earlier found only in visual paradigms, generalize to the auditory sensory system. We also observed suppression of the low beta activity to CS+ in aversive conditioning over the hemisphere contralateral to expected electrical shocks, presumably indicating preparation of the somatosensory system to the expected nociceptive US.